We propose to develop a resource to examine the biochemical basis of genetic susceptibility to lung cancer. We will identify identical twins of lung cancer patients and start long-term lymphocyte lines from these identical twins and from two other matched groups, one representing the normal population and one representing the population of lung cancer patients without the complicating interferences of disease. With these lines, carcinogen metabolism and DNA repair can be examined to see if the lung cancer population differs from normal. These lines will be available to any investigator who wants them. We ourselves propose to use them to measure benzo(a)pyrene metabolism and the P450 proteins. In collaboration with others, we will also measure epoxide hydrase, conjugating enzymes, the carcinogen receptor protein responsible for induction of aryl hydrocarbon hydroxylase, and DNA repair capacity.